Aircraft are commonly equipped with Cabin Pressure Control Systems (CPCSs), which maintain cabin air pressure within a desired range to increase passenger comfort during flight. A representative CPCS may include a controller, an actuator, and an outflow valve. The outflow valve is fluidly coupled between the aircraft's cabin and ambient pressure (referred to herein as “ambient”). During operation, the controller commands the actuator to move the outflow valve between various positions to control the rate at which pressurized air from the aircraft's cabin is vented to ambient. The controller may command the actuator to modulate the outflow valve in accordance with a predetermined schedule or, perhaps, as a function of one or more operational criteria; e.g., as a function of cabin pressure as monitored by a pressure sensor operatively coupled to the controller. By actively modulating the outflow valve in this manner, the controller may maintain the aircraft's cabin pressure within a desired range. Furthermore, the outflow valve may be position such that the pressurized air exhausted thereby provides additional forward thrust to the aircraft.
One known type of outflow valve commonly deployed within cabin pressure control systems is a multi-door outflow valve. The multi-door outflow valve may include, for example, a frame, a first door (e.g., a first rectangular butterfly plate) pivotally mounted to a first portion of the frame, and a second door (e.g., a second rectangular butterfly plate) pivotally mounted to a second portion of the frame. The multi-door outflow valve may be mounted in the aircraft fuselage such that the second door is closer to the aircraft's tail than is the first door; for this reason, the first door and the second door may be referred to herein as the “forward door” and the “aft door,” respectively. The forward and aft doors may be mechanically linked by one or more linkages such that the forward and aft doors collectively move between an open position, a closed position, and various intermediate positions. In the open position, the forward and aft doors permit pressurized air to flow from the aircraft's fuselage, and thus from the aircraft's cabin, to ambient. In the closed position, the forward and aft doors each sealingly engage an inner periphery of the frame, and the forward door sealing engages a portion of the aft door, to generally prevent pressurized air airflow from the fuselage to ambient.
Ideally, multi-door outflow valves of the type described above are lightweight, operate in a quiet manner, and provide substantially complete sealing when closed. In addition, when utilized for thrust recovery, it is desirable for such outflow valves to encourage rapid airflow there through to optimize the production of forward thrust in the partially open or cruise position. To this end, certain multi-door outflow valves have been produced that include a cylindrical bellmouth affixed to the inner sealing edge of the forward door (i.e., the edge of the forward door that sealingly engages the aft door in the closed position). When the outflow valve is in the partially open or cruise position, the cylindrical bellmouth conditions the airflow through the outflow valve to produce a relatively smooth laminar flow. The cylindrical bellmouth consequently decreases the production of noise and increases the production of forward thrust in the open position. These advantages notwithstanding, conventional outflow valves including cylindrical bellmouths are limited in certain respects. The provision of the cylindrical bellmouth increases the overall weight of the outflow valve and may add undesirable complexity and cost to manufacturing processes. Additionally, the provision of the cylindrical bellmouth increases the stiffness of the forward door. In so doing, the cylindrical bellmouth hampers the ability of the forward door to flex along with the more-flexible aft door, which, in turn, negatively impacts the sealing characteristics of the outflow valve in the closed position.
Accordingly, it is desirable to provide an outflow valve suitable for deployment within an aircraft's cabin pressure control system that overcomes the above-described limitations. In particular, it would be desirable to provide an outflow valve (e.g., a multi-door outflow valve) that is relatively lightweight, that operates in a quiet manner, that conditions airflow to increase forward thrust production, and that has superior sealing characteristics when closed. Other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.